It is known the methods for studying various objects involving formation of an image of the object's structure by exposure of the objects to a flux of neutral or charged particles (neutrons, electrons, gamma-quanta, X-rays, etc.), and registering the distribution of the radiation intensity resulting from interaction with the object. The thus-formed image is interpreted as the distribution of interaction properties between the object and the radiation used, these properties being inherent in the various elements of the object, in particular, as a two-dimensional projection of a spatial distribution of attenuation of the radiation resultant from the transmission through the object (cf. the textbook Production Automation and Industrial Electronics (Moscow, Sovetskaya Entsiklopediya PE, 1964, v. 3, p. 277, v 1, p. 209 (in Russian))
Similar methods are also known in electrons, X-ray, and other types of lithography for forming a preset pattern corresponding to a known structure of a specially made object (i.e. stencils mask); (cf. e.g., Electronics: An Encyclopedic Dictionary. (Moscow, Sovetskaya Entsiklopediya PE, 1991, pp. 254-255 (in Russian)).
The above methods are performed by devices, having a radiation source, a means for placing an object such that it may be exposed to the radiation such as a holder, and a means for image recording which is sensitive to radiation resulting from the interaction of the source-emitted radiation and the object such as a detector.
However, capabilities of said methods are limited unless use is made of a means for controlling a primary particle flux or a flux resulting from interaction with the object. In particular, there is a need for controlling the spectrum, direction, width, divergence, and other beam parameters of the radiation beam.
Some prior-art radiation methods for producing the image of an object are known to use the concept described before are performed with the aid of optical elements which are capable of solving some of the problems mentioned before, in particular, controlling the beam width and selecting the particles that have deviated from a preset direction (cf. Physics of Image Visualization in Medicine, edited by S. Webb, the Russian translation published in Moscow (Mir PE, 1991, pp. 41, 101, 134)). Setting aside the fact that the problems thus solved bear a specific nature, it is also worth noting that the concepts used in these methods involve the use of a radiation source having surplus intensity
Use of other types of optics in the devices of the character discussed herein is addressed in the symposium "X-ray Optics and Microscopy", edited by G. Schmahl and D. Rudolph (Moscow, Mir PE, 1987), wherein there are considered, in particular, use of Fresnel zone plates for beam focusing (id. at p.87), and grazing-incidence mirror optics (id. at p. 174). However, Fresnel zone plates are characterized, due to the specific features of the physical concept applied, by an extremely high selectivity as for particle energy (wavelength), and for this reason such plates cannot be used for controlling a broad-spectrum radiation. In addition, as is noted in the symposium text, these plates should have a very small size and the devices making use of these plates feature a small angular aperture and a low aperture ratio. As far as mirror optics is concerned, while these optics have practically acceptable geometric dimensions, they are capable, as a rule, of only a single reflection, this being due to extremely low magnitudes of the angle of total external reflection effective for the radiation of the ranges under discussion. Thus, the devices that make use of such optics feature only restricted possibilities for controlling radiation beams, as well as an extremely small angular aperture which corresponds to too low magnitudes of the angle of total external reflection.
One more prior-art device for producing the image of an object (U.S. Pat. No 5,175,755 issued Dec. 29, 1991) is of another design. This device makes use, for controlling a radiation beam, of an optical system which appears as a lens established by a set of channels having reflecting walls and which is adapted for radiation transport. A variety of modes of controlling a flux of particles are provided in the device. In particular, the transformation of a divergent radiation into a quasi-parallel one before exposing an object to the radiation, transporting a broad-spectrum radiation in conjunction with a possibility of cutting-off the hard radiation component, and transforming the size of the resultant image.
U.S. Pat. No 5,192,869, issued Mar. 9, 1993 discloses the construction of a lens for transforming a flux of neutral or charged particles which can also be used for controlling a flux of particles and is also suitable for use as a component part of a device for producing the image of an object. The lens makes use of rigid supporting elements spaced apart from one another lengthwise so as to provide a rigid fixing of the channel-forming elements at places where they pass through holes in the supporting elements. An appropriately selected arrangement of the holes enables the attainment of the correspondence of the axial lines of individual channels to the generating surfaces of a required shape. In order to meet the condition of the radiation transport along the channels without a considerable loss, the cross-sectional dimensions of each individual channel must be as small as possible. However, the aforementioned construction, involving the use of a mechanical assembly procedure, sets limits on the minimum channel cross-sectional dimension. In particular, with radiation transport channels made of glass capillaries or polycapillaries having a diameter on the order of 300 microns, the glass tends to lose the properties required for proper assembling. Thus, the capillaries or polycapillaries start "soaring" in the air. They cannot be given a required radius of curvature during assembling, and the capillaries are liable to sag between the points of support. Such a restriction for their diameter results in the radiation losing the ability to focus into a spot having a diameter smaller than the capillary inside diameter or the polycapillaries outside diameter. The least focal spot diameter attainable with such lenses is 0.5 mm, which means that it is impossible to provide a high concentration of radiation due to too large a focal spot diameter.
A finite size of the channels imposes limitation on the range of energies used. With a preset focal length f, even though the radiation source is point-like, a minimum angle of radiation incident on the capillary peripheral zone is .theta.=d/2f, where d is the channel diameter.
To provide an efficient radiation transfer, it is desirable that the parameter .theta. approximate or even be less than the critical angle of reflection .theta..sub.c because the critical angle decreases as the energy increases This condition restricts the use of high energies in lenses of first and second generations For instance, with an X-ray energy E=10 keV, radiation capture into the channel is not in excess of 15%, and, with an increase in the focal length, the capture angle decreases, and hence the efficiency of the system decreases, too. It follows that it is necessary to use radiation transfer channels having cross-sectional dimensions of microns and submicrons This is impossible, due to the aforementioned reasons, with the construction described before and involving the use of mechanical assembling during the manufacture.
Mechanical assembling is also the cause of another disadvantage. Angular divergence is determined by the expression .DELTA..theta.=.DELTA.L/L, where .DELTA.L is the sum of variations of capillary diameter and the diameter of a hole in the support disk, L is to the distance between the disks which is not to exceed 1-3 cm. With a .DELTA.L being about 10% of the diameters and the value of the L on the order of 500 microns, .DELTA..theta. is on the order of 5.multidot.10.sup.-3 rad which is typically unacceptable.
The aforedescribed device and lens as taught in U.S. Pat. Nos. 5,175,755 and 5,192,869, respectively, have capabilities which are restricted, apart from the factors mentioned before, also by the fact that they utilize only the channeling properties of individual channels functioning independently of one another. In this case, the wave properties of the particles being channeled are exhibited only when the particles are reflected from the channel walls during their transfer along the channels. This is due to the fact that no measures are taken in the lens construction for displaying the effect of interaction between particles after their having been transferred along the different channels. This limits the attainable degree of radiation concentration to the geometric accuracy of the orientation of the channels towards a desired point. It also precludes energy separation of particles, and thus monochromatization of the radiation with the aid of the lens itself, in the absence of any other means.
The restrictions stated above affect adversely the capabilities of the device for producing the image of an object which has an optical system in the form of a lens built up of a set of channels having reflecting walls for radiation transfer In particular, these restrictions preclude any increase in the resolution of the devices reduction of the radiation load that the object under examination is exposed to, and the use of a lower-power radiation source.